Bolt rethreading apparatus



July 6, 1948. c, HARD"; 2,444,662

BOLT RE-THREADING APPARATUS Filed Oct. 3, 1945 r 2 Sheets-Sheet l Inventor Julyfi, 1948- G. c. HARDIE BOLT RE -THREADING APPARATUS 2 Sheets-Sheet 2 Filed Oct. 3, 1945 Patented July 6, 1948 UITED STATES PATENT OFFICE BOLT RETHREADINGAAPPARATUS GeorgeC. Hardie, Brooklyn, N. Y.

Application October 3, 1945, Serial-No. 619,971

3 Claims. 1

This invention relates to an apparatus for rethreading a plurality of bolts when the threads of the latter have become worn or mutilated.

The primary object of the present invention is to provide an apparatus of the above kind which is comparatively simple in construction and efficient in operation, and which includes a bolt re-threading machine embodying a plurality of holders for threading dies and a drive shaft for said die holders adapted for driving connection with the power driven tool shaft of a drill press or like machine.

A more specific object of the invention is to provide for convenient assembly of the parts of the re-threading machine and removal of the die holders so that a plurality of die holders of difierent sizes may be readily interchangeably employed.

Still another object of the invention is to provide a re-threading machine adapted for simultaneously re-threading a plurality of adjacent stud bolts fixed in a machine frame orother structure.

Yet another object of the invention is to provide an apparatus of the above kind including simple and efficient means for effectively holding a plurality of headed bolts in; position to be threadedby the re-threading machine forming part of the apparatus.

Specific features and additional objects of the present invention will become apparent from the following description when considered in connection with the accompanying drawings, in which:

Figure 1 is a View, partly in elevation and partly in section, of a bolt i e-threading machine form- Figure 5 is an end elevational view of one of the die holders, looking at the inner end thereof. Figure 6 is a plan view of the die retaining ring forming part of each die holder.

Figure 7 is a fragmentary perspective view showing one side portion of the frame of the.

re-threading machine.

Figure 8 is a transverse section taken on line 88 of Figure 1.

' Figure 9 is a developed perspective view,"partly broken away; and showingthe' devicefor'holding' a plurality orheaded'bolts forbeing re-threaded .by the useof the machine: shownin: Figure 1.

Figure 10 is a fragmentary top planview of the device shown in Figure 9, with the-parts thereof headed .bolts.

. Referring in detail to the drawings, the-presentapparatus includes a boltre-threadingfmachine as disclosed in Figures 1 to-8,; inclusive, such machine-including, a substantially ,U -shaped frame 5 having a pair of spacedbearings 6; at each, end and a further bearing 1 .midway between its ends. The bearings 6 project inwardly and are preferably of U-shape so as ,tobeopen at their inner sides as at 8. A driven shaft 9 is journalledin each pair of bearings- 6,: and a pinion i0 is secured on each driven shaft 9land disposed between the associated pair of bearings 6. A drive shaft H is-journalled in the; bearing 1 and is adapted to have its outer end connected to and driven by the powerdriven tool .shaft of a drill press or like machine. For thelatter purpose, the shaft ll; hasa squared ou-ter end I2 fitted and welded-within the inner portion of the similarly shaped bore 13. of a; polygonal head I4. Thehead i l is adapted to be received and secured in the chuck of the power driven tool shaft of the machinewithwhich the present threading machine is used, or the outer portion of the bore l3 .forms a socket for reception of the driving end of atool shaft of different type, aset screw l5 being provided tosecure the head M on said end of the tool ,shaft- A gear 16 is secured onthe inner end of, the drive shaft II and disposed between andin meshwith the pinions in so .as to maintain the drivenshafts 9 in their bearings 6. ;The.shaft H is longitudinally slidable in the bearing 1,. and is releasably held with the head M adjacentthe; bearing 1 and with the, gear 16 betweenthepinions III by means of a collar I! having a-set screw 18 which may be loosened-to permit sliding of :the shaft ll outwardly. .When the latter. is done, the gear lt willabe withdrawn from between the pinions .m so that-the driven shafts 9 may be detached or withdrawnfroms, the bearings 6,

therebyfacilitatingqcompact storage of the, ma-

; chine when not in use. A reversal of this operato its driven shaft.

the die holders may be: readily removed so as to each .die holder, while a bolt guide ring 24 is fixed in the bore of the die holder intermediate the ends of said bore. The guide ring 2| effectively guides the bolt being re-threaded so that it will be maintained truly axially of the die and holder during the re-threading operation, the bolt passing into the bore 20 as the operation proceeds. In order to hold the die 23 in place, a retaining plate 25 is bolted to the inner end of each die holder and is provided with a central opening 26 for the free passage of the bolt therethrough to the die 23. The die holder I9 has cars 21 adapted to be registered with cars 28 of the retaining plate 25 for reception of bolts 29 by means of which the plate 25 is secured in place to retain the die 23 within the socket 21. Each die holder 19 is provided at its outer end with a reduced polygonal shank 30 removably fitted in a similar socket 3! provided in the inner end of the associated driven shaft 9, and a cross bolt 32 is extended through the shank 30 and the shaft 9 to secure the die holder It will be apparent that permit the interchangeable use of die holders of different sizes. Also, the dies may be removed from the die holders so as to permit the interchangeable use of a limited number of different sized dies with each die holder, thereby adapting the machine for use in connection with bolts of different sizes.

When the present machine is used for rethreading stud bolts anchored in a machine frame or other structure, driving engagement is effected between the shaft H and the power driven tool shaft of a drill press or like machine. The present machine is then fed downwardly relative to the bolts as the shaft H is rotated for turning the die holders [9 in the same direction as indicated by the arrows in Figure 2. Two adjacent stud bolts aanchored in a machine frame I) may thus besimultaneously 're-threaded by use of the machine as shown in Figure 1, each stud bolt a passing into and being rethreaded by the die 23 of a different one of the two die holders l9. Dif-.

'ferent models of the present machine may be any two of the stud bolts of that particular existing machine or structure. Upon completion of the re-threading operation, the dies 23 may be threaded off of the stud bolts by simply reversing the direction of rotation of the tool shaft so that the shafts H and 9 will be reversely driven. The

machine has been found especially useful in rethreading the stud bolts of conventional superheater headers and of economizer heads.

In order to adapt the present machine for use in rethreading headed bolts which are not anchored in a machine frame or other structure as is the case with stud bolts, I have provided a special form of bolt holding device as shown in Figtires 9 and 10. This bolt holding device includes an elongated bar 35 adapted to be mounted edgewise vertically and in a horizontal position upon an end of the top of a bench or the like, said bar being provided with depending end leg extensions 36 formed with enlarged lower ends 31 protion for use. The bar as is provided with a longitudinal series of uniformly spaced openings 39 for the passage therethrough of the stems of the bolts 40 to be re-threaded, the spacing of the openings 39 corresponding to the spacing of the die holders l9 of the re-threading machine. The bar is provided on the back thereof with a plurality of equally spaced projecting fiat sided lugs 41. An opening 39 is provided centrally between each pair of adjacent lugs 4|, and the latter are so spaced as to snugly receive the heads of the bolts 40 therebetween with the fiat adjacent sides of adjacent lugs 4| engaging opposite sides of the bolt heads so as to effectively restrain the bolts against turning while being re-threaded. In order to firmly hold the bolts in place with the heads thereof between adjacent ones of the lugs 4| and so that the bolts may not be forced backwardly out of the openings 39 during the rethreading operation, a clamping bar E2 is bolted to the back of the bar 35 so as to extend across the lugs 4| and the heads of the bolts 40 as illustrated in Figure 10. The bars 35 and 42 are provided with a plurality of openings as respectively indicated as 43 and 46 for reception of clamping bolts as illustrated at 45 in Figure 10, whereby to effectively bolt the bar 42 to the bar 35 at the back of the latter for securing the bolts 43 in place as above described. In this way and by this means, a plurality of the bolts 40 ma be supported and held in pairs for being successively re-threaded by use of the machine shown in Figure 1. After the re-threading operation has been completed in connection with all of the bolts supported and held by the device shown in Figures 9 and 10, the bar 42 may be unboltcd from the bar 35 so as to permit removal of the re-threaded bolts 40 from said bar 35.

From the foregoing description, it is believed that the construction, operation and advantages of the present invention will be readily understood and appreciated by those skilled in the art. Minor changes may be made in details of construction illustrated and described, such as fall within the scope of the invention as claimed.

What I claim is:

1. In a bolt re-threading apparatus, a rethreading machine comprising a substantially U-shaped rigid frame having a pair of forked inwardly facing spaced and aligned integral bearings at each end and a further integral bearing midway between its ends, a driven shaft journalled in each pair of bearings, a pinion secured on each driven shaft between the associated pair of bearings, a drive shaft journalled and longitudinally slidable in said further bearing and having an outer end adapted for driving connection with the power driven tool shaft of a machine, a gear secured on the inner end of said drive shaft and disposed between and meshing with the pinions of the driven shafts, a hollow die holder secured to the inner end of each driven shaft, and a bolt re-threading die secured in the inner end of each die holder.

2. The structure defined in claim 1, wherein each driven shaft is provided with a polygonal socket at its inner end, each die holder having a reduced polygonal shank at its outer end removably received in the socket of the associated driven shaft, and means operatively associated with and removably securing the shank of each die holder in the socket of its associated driven shaft.

3. In a bolt re-threading apparatus, a rethreading machine comprising a substantially U-shaped rigid frame having a pair of inwardly projecting spaced and aligned integral bearings at each end and a further integral bearing midway between its ends, said spaced bearings being forked and open at the inner sides thereof, a

driven shaft journalled in each pair of bearings and removable from the latter upon being shifted laterally inwardly, a pinion secured on each driven shaft between the associated pair of bearings, a drive shaft journalled and longitudinally slidable in said further bearing and having an outer end adapted for driving connection with the power driven tool shaft of a machine, a gear secured on the inner end of said drive shaft and disposed between and meshing with the pinions of the driven shafts, means operatively associated with and releasably securing the drive shaft against longitudinal movement relative to the frame, said last-named means being releasable to permit outward longitudinal movement of said drive shaft so as to withdraw the gear from between the p'inions and permit the removal of the drive shafts with their pinions from said spaced bearings, a hollow die holder secured to the inner end of each driven shaft, and a bolt re-threading die secured in the inner end of each die holder.

GEORGE C. HARDIE.

REFERENCES CITED The following references are of record in the Linderme Aug. 25, 1942 

